RE: RMAN guru question

Dennis:

>> I assumed the same as you, that RMAN writes its most
>> recent information to the control file as well as the catalog (there is a
>> retention parameter, so watch that).

This should be the case. The current database control file should always be current (assuming you
have not used an old backup control file or re-created the control file which would, of course,
result in the creation of a new database incarnation). Of course, your catalog can get out of sync
in some cases (infrequently if you are using RMAN right though).

>> One thing I have learned from disaster recovering RMAN is that you need
>> to write a copy of the control file to the backup tape. While RMAN will
>> backup the control file, it can't create it if there is no control file
>> present.

Actually in 9i that's not quite true. In 9i you can recover the spfile and the control file
from the backup before mounting the database, no control file required. There are a couple of different ways of doing this depending on the situation (such as
if you are using autobackup of control files or not and if you have recovered the
control file backups or if you need to get a control file backup off of tape).

You can also recover the control file from the backup in Oracle 8i (or 9i) manually using the
dbms_backup_restore procedure. You can find the instructions on how to do this
in the 9i docs (but it applies to 8i as well), or on metalink or in my Mastering
Oracle8i book or my upcoming RMAN Backup and Recovery book... It's not easy the
first time, but it works and once you are used to it it's not so bad.

Of course, having a recovery catalog makes the control file restore much easier...

Robert G. Freeman - Oracle OCP
Oracle Database Architect
CSX Midtier Database Administration
Author
Oracle9i RMAN Backup and Recovery (Oracle Press - Oct 2002) Oracle9i New Features (Oracle Press)
Mastering Oracle8i  (Sybex)

The avalanche has begun, It is too late for the pebbles to vote.

-----Original Message-----
Sent: Thursday, August 08, 2002 4:26 PM
To: Multiple recipients of list ORACLE-L

Joe - I have been working on a disaster test for RMAN so we can quit doing weekly cold backups. I assumed the same as you, that RMAN writes its most recent information to the control file as well as the catalog (there is a retention parameter, so watch that). I tested no catalog recovery (just the control file) with a small practice database and it worked fine. Then I tried it with one of our production databases (recovering on a test system). RMAN ran for awhile, creating data files, and then stopped. I didn't get that issue debugged. Instead on my next try I loaded the RMAN catalog and went that route. Got interrupted on another project and haven't gotten back to it.

    One thing I have learned from disaster recovering RMAN is that you need to write a copy of the control file to the backup tape. While RMAN will backup the control file, it can't create it if there is no control file present. RMAN must first mount the database and it can't do that unless the control file is there. Once it has the database mounted, then RMAN can refresh the control file.

    My experience applies to Oracle 8.1.6, using disk file backups. Dennis Williams
DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Thursday, August 08, 2002 2:57 PM
To: Multiple recipients of list ORACLE-L

I've tested this and it works, i'm looking for verification of theory.  

1. built 2nd db for repository.
2. built repository and registered db
3. full backup via rman.
4. disconnect from RMAN
5. reconnect only to target
6. shutdown/startup mount target
7. restore database. It states, using controlfile.
8. recover database.

all looks good. my question is even though i'm using a catalog during my backup and simulate a total loss of that db by NOT connecting to a catalog during restore, it was able to get the info from the control file.  

IS this default behavior, that when using RMAN, the control file is ALWAYS written to even if a catalog is being used during the backup phase?  

Is this a safety net for those who might not be backing up their repository database?  

thanks, joe  

ENV: linux rh 7.3, oracle 9.2.0.1  

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